There is a fundamental tradeoff in photovoltaics between (1) flat-plate systems, which can collect both direct and diffuse (off-axis) components of sunlight but require a large area of semiconductor material, and (2) concentrator systems, which use small areas of very high-efficiency solar cells, but typically use only the direct component of sunlight. It should be noted that concentrator systems must also be pointed very accurately at the sun or other light source, and off-axis light outside of a certain acceptance cone is typically wasted. In addition, high-efficiency multijunction III-V cells commonly need to be mounted in a costly, labor-intensive process in discrete receivers.
Currently, flat-plate photovoltaic systems use a large amount of semiconductor area, thereby restricting the type of solar cells used in flat-plate systems to low-cost, relatively low-efficiency cells, such as silicon flat-plate cells. Concentrator photovoltaic (CPV) systems allow small-area, high-efficiency multijunction III-V cells to be used economically, but typically use only the direct portion of the solar spectrum. Depending on the location, approximately 15 to 40 percent of the energy in sunlight may be diffuse, causing this energy to be lost to CPV systems. The power output of standard CPV systems, whether for terrestrial or space applications, or solar, laser power, or other applications, drops to near zero for off-axis light, whether that light is diffuse light from well outside the sun's disk, or light from the main light source that is off-axis relative to the CPV optics due to misalignment of the CPV optics. Additionally, packaging III-V cells in discrete packages is slow and costly.
As such, there is need for an improved photovoltaic system and method to collect both direct light and diffuse light.